Herein, a highly selective and sensitive fluorescent sensing system is developed for the accurate quantitative determination of γ-Hexachlorocyclohexane (γ-HCH, Lindane). With carboxyl-functionalized CdSe/ZnS core–shell quantum dots (QDs) as the substrate, 3-Aminophenylboronic acid (3-APBA) is covalently conjugated onto the quantum dot surface via an amidation reaction. Systematic characterizations are used to confirm the successful fabrication of the CdSe/ZnS-COOH@3-APBA fluorescent probe, which exhibits excellent luminescence properties and superior colloidal dispersion stability. Under optimal experimental conditions, an increased γ-HCH concentration induces gradual attenuation of the probe fluorescence intensity. A favorable linear correlation is achieved within 10–140 nM, and the limit of detection is 2.62 nM. Mechanistic studies reveal that γ-HCH binds to 3-APBA on the probe surface via halogen bonding to form non-fluorescent ground-state association complexes, thereby triggering static quenching of the probe. This method can effectively distinguish α-, β-, and δ-hexachlorocyclohexane isomers. With the merits of simple operation, high sensitivity, excellent stability, and strong anti-interference capability, it provides a new strategy for the rapid screening and accurate quantification of γ-HCH residues in environmental and food matrices.
Zhaofa Li,Quanxiu Zhou,Palanivel Sathishkumar,Liang Peng,Qunfang Wang,Feng Long Gu
The present work fabricated a novel dual-emission responsive ratiometric fluorescent hybrid nanoprobe using a mixture of blue fluorescence-emitting N-Doped Carbon Quantum Dots (N-CQDs) and red fluorescence-emitting l -cysteine-capped CdSe/ZnS Quantum Dots (Lcys-CdSe/ZnS QDs). The addition of Cu 2+ resulted in the strong and specific fluorescence quenching in Lcys-CdSe/ZnS QDs while N-CQDs retained their fluorescence intensity. Further exploration of the nanoprobe showed that the detection limit was 3.78 × 10 −9 M and the linear range was below 3.2 × 10 −6 M. The nanoprobe possessed excellent anti-interference in the Cu 2+ determination and its application was successful in natural water samples. Experimental results suggested that the superficial left cysteine (Lcys) combines with Cu 2+ causing static quenching. Results of density functional theory (DFT) computation explained that Cu 2+ has the greatest possibility to combine with surficial Lcys and furthermore illustrated the role of the combination in static quenching. The work showed one of origin of the selectivity of the nanoprobe and a potentially guidance to design high selective ratiometric fluorescent nanoprobes.
In this study, a ratiometric fluorescence nanoprobe is developed for the analysis of hydrogen peroxide (H 2 O 2 ). Silver nanoclusters (AgNCs) were synthesized by chemical reduction method using sodium borohydride (NaBH 4 ) as reducing agent, and were coupled with CdSe/ZnS quantum dots (QDs) to form the ratiometric fluorescence nanoprobe silver nanoclusters-quantum dots (AgNCs-QDs). The effect of the volume ratio of CdSe/ZnS QDs to AgNCs on the fluorescence ratio of AgNCs-QDs was investigated. The fluorescence characterization results show that two emission peaks of AgNCs-QDs are located at 473 nm and 661 nm, respectively. Transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) results show that H 2 O 2 can cause the fluorescence probe to aggregate, while etching AgNCs to produce silver ions, which together cause the fluorescence of the QDs in the ratiometric fluorescent probe to be quenched. Based on this strategy, the fluorescence intensity ratio of the two emission peaks F 473 /F 661 exhibits a strong linear correlation with the concentration of H 2 O 2 . The detection range is 3.32 µM ~ 2.65 mM with a detection limit of 3.32 µM. In addition, the ratiometric fluorescence probe can specifically recognize H 2 O 2 and has excellent anti-interference performance and good fluorescence stability. Importantly, the probe was utilized for the detection of H 2 O 2 in serum, showing the possibility of the probe in clinical detection applications.
The nanostructured hybrid assembly has gained growing interest due to their unique electronic, optical and catalytic properties . Herein, a novel ratiometric fluorescent sensor was constructed by coupling blue-green emission carbon dots (CDs) to a block copolymer micelle-encapsulated red-emission CdSe/ZnS QDs through host-guest interaction. The carbon dots (CDs) were prepared by carbonization of β-cyclodextrin (β-CD) via a simple hydrothermal process. The amphiphilic diblock copolymer AZO-PNIPAM-b-P(St-co-MQ) containing azobenzene (AZO)-terminated hydrophilic poly( N -isopropylacrylamide) (PNIPAM) block and hydrophobic polystyrene (PS) block was synthesized by a typical RAFT polymerization . The 5-(2-methacryloylethyloxymethyl)-8- quinolinol (MQ) units were introduced into PS block, which could make CdSe/ZnS QDs to be embedded into the core of the block polymer micelles via coordination interaction in the self-assembling process. The as-fabricated β-cyclodextrin derived CDs-coupled block copolymer hybrid micelles loaded with CdSe/ZnS QDs as a fluorescence sensor exhibited dual emission peaks of CDs centered at 450 nm and CdSe/ZnS QDs at 620 nm with a large peak separation of 170 nm upon excitation at 360 nm. And the as-prepared hybrid micelles as a ratiometric fluorescence sensor can be applied to detect Hg 2+ and Cu 2+ with the detection limits down to 1.6 and 2.74 μM, respectively.
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